Picosecond electrical pulses have many applications, including clocks for high-speed analog-to-digital converters (ADC) and high-speed circuit component characterization using time-domain-reflectometry (TDR).
Known approaches to generating picosecond electrical pulses include: nonlinear transmission lines (NLTL) as described by, for instance, Rodwell et al. in “Active and nonlinear wave propagation devices in ultrafast electronics and optoelectronics,” Proc. IEEE, vol. 82, no. 7, pp. 1037-1059, 1994 and by Birk et al. in “Efficient transient compression using an all-silicon nonlinear transmission line,” IEEE Microwave and Guided Wave Letters, vol. 8, no. 5, pp. 196-198, 1998. Other approaches include transmission line discontinuities as described by, for instance, Frankel et al. in “Picosecond pulse formation by transmission line discontinuity,” Electronic Letters, vol. 25, no. 20, pp. 1363-1364, 1989[5]; and photoconductive switching as described by, for instance, Takakata et al. in “3.3 ps electrical pulse generation from a discharge-based metal semiconductor-metal photodetector,” Electronics Letters, vol. 41, no. 1, pp. 38-39, 2005.
These methods exploit the electromagnetic properties of passive circuit components to produce fast signals. It can be difficult to implement these circuits using CMOS technologies on a CMOS semiconductor substrate even though all-silicon NLTLs to sharpen the signal rise edges to 8-ps have been reported by Mohammed et al. in “A novel silicon schottky diode for NLTL applications,” IEEE Transactions on Electronic Devices, vol. 52, no. 7, pp. 1384-1391, 2005.
Digital circuits can be used to generate short-pulses, but the pulse widths of the output pulses are determined by the speed of the transistors used in the digital circuits. A bench-mark for pulse-duration of the generated pulses is the fan-out-of-four (FO4) propagation delay of corresponding inverter gates. An exemplary FO4 delay corresponds to about 50 ps for the present technology.
Nanosecond and sub-nanosecond electrical pulses have been generated through a few other techniques, such as those circuits for ultrawide-band (UWB) applications disclosed in, for example, J. Han et al, “On the development of a compact sub-nanosecond tunable monocycle pulse transmitter for UWB applications,” IEEE Transactions on Microwave Theory and Techniques, pp. 1-9, 2006, and various pulsed-power circuit topologies. These techniques also exploit the properties of transmission lines. However, on-chip applications of these techniques and their picosecond pulse generation capabilities have not previously been reported.
All of the foregoing publications are hereby incorporated by reference for all purposes.
There is a need for a picosecond pulse generator circuit that can be implemented on a common semiconductor substrate, such as a CMOS semiconductor substrate. While various implementations of picosecond pulse generation circuits and systems have been developed, no design has emerged that generally encompasses all of the desired characteristics as hereafter presented in accordance with the subject technology.